Recently, pressure infiltration was used to fabricate alumina particulate (Al{sub 2}O{sub 3p})-reinforced Al matrix composites, and a program is in progress to demonstrate the suitability of this material for use in automobile parts with the goal of reducing the weight and increasing the vehicle performance. Mechanical behavior and damage mechanisms of an Al{sub 2}O{sub 3} particulate-reinforced Al matrix composite (Al{sub 2}O{sub 3p}/Al) prepared by pressure infiltration are investigated and compared with those of a cast ductile iron. In addition to low cost and reduced weight, the composite has a Young`s modulus comparable to the ductile iron, However, its fracture toughness is lower than that of the ductile iron. Interface debonding between the graphite and ferrite is responsible for the crack initiation behavior of the ductile iron. The crack in the ductile iron is arrested by the ductile ferrite phase surrounding the graphite, leading to high fracture toughness. For the Al{sub 2}O{sub 3p}/Al composite, the dominating crack initiation mode is particulate cracking. Interface debonding and zigzag cracking of particulates are additional fracture modes. The high content of Al{sub 2}O{sub 3} particulates and the high thermal and elastic incompatibilities between the Al matrix and Al{sub 2}O{sub 3} particulates result in brittle fracturemore » and low fracture toughness for the composite. Possible ways to increase the fracture toughness of the Al{sub 2}O{sub 3p}/Al composite material are also outlined.« less